What Are Cardiac Enzymes?

If your doctor suspects that you’re having a heart attack or that you may have had one recently, you may be given a cardiac enzyme test. This test measures the level of certain proteins circulating in your bloodstream.

Higher levels of these chemicals — known as biomarkers — are released when the heart muscle is damaged.

The protein troponin T is the key biomarker measured in a cardiac enzyme test. This biomarker helps let your doctor know when your heart has been under stress. It can also reveal if your heart muscle isn’t getting enough oxygen.

Keep reading to learn more about the testing process and what the results may mean for you.

A cardiac enzyme test doesn’t require any preparation. You don’t have to fast or stop taking certain medications.

In many cases, cardiac enzymes are measured in an emergency situation when a person is suspected of having a heart attack. You or someone close to you should tell your doctor about any medications and supplements you take.

Your doctor should also know any other important medical information, including:

A blood test for cardiac enzymes is like a standard blood test. A small vial or two of blood is filled through a needle inserted into your arm. There may be a little pain when the needle is inserted.

Your doctor will assess your biomarker levels to confirm whether you’ve had a heart attack and assess how much damage the heart muscle has endured. They’ll often check them more than once to see if the levels are changing.

In addition to checking your biomarkers, your doctor may also want to get other information from your blood.

This includes your:

cholesterol levels

blood glucose (sugar) levels

white and red blood cell count, as well as your platelet levels

levels of electrolytes, such as sodium and potassium

levels of B-type natriuretic peptide (BNP), a hormone that can indicate heart failure

Test results of your cardiac enzymes can indicate whether it’s likely you had a heart attack. For example, most healthy, young people have no troponin T circulating in their bloodstream. The more damage the heart muscle has suffered during a heart attack, the higher the levels of troponin T circulating in your blood.

Cardiac troponin T is measured in nanograms per milliliter (ng/mL). If your troponin T level is above the 99th percentile for the test being used, your doctor will likely diagnose a heart attack. Levels that start high and fall suggest a recent injury to the heart. It could have been a mild heart attack. You may not have even been aware of it.

Cardiac enzyme test results are usually available within an hour of the blood sample being drawn.

Cardiac enzyme levels can rise for reasons other than a heart attack. For example, sepsis, a type of blood infection, can lead to elevated troponin levels. The same is true for atrial fibrillation, a common heart rhythm problem.

Because other factors can produce higher cardiac enzyme levels, your doctor won’t rely on your enzyme levels alone to diagnose a heart attack. Your doctor will also use an electrocardiogram to confirm a diagnosis.